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Coroplast Sandwich Hull

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  • rwdavis0
    Having just ordered the FD plans last week I m sorting through the options and thinking about construction.Has anyone any thoughts on using 1/4 coroplast
    Message 1 of 12 , Aug 4, 2007
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      Having just ordered the FD plans last week I'm sorting through the
      options and thinking about construction.Has anyone any thoughts on
      using 1/4" coroplast (corrugated plastic panels used for signs,
      greenhouses, etc.) sandwiched between 1/8" plywood for the hull?

      If the edges were caulked I imagine some additional bouyancy would be
      added, although 1/2" total thickness might be too much to lace
      together. Maybe just just 1/8'ply on the outside/ coroplast in the
      middle and Dacron fabric in the inside for 3/8'+ thickness?

      Bob Davis
      (ps. I have (3) 4x8 sheets of coroplast in the garage for a greenhouse
      project that I hope my wife has forgotten about.)
    • Bill
      I had thought about laminating coroplast (actually, I did not know what it was called) with Dacron on an earlier boat design but without laminating it to
      Message 2 of 12 , Aug 4, 2007
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        I had thought about laminating coroplast (actually, I did not know
        what it was called) with Dacron on an earlier boat design but without
        laminating it to plywood. It is also known as fluted polypropylene. I
        believe the sample I had was 1/8", and it comes as thin as 2mm. Never
        got around to trying it and do not have any on hand at the moment to
        experiment with.

        Info here:
        http://www.coroplast.com/

        This fellow has some construction ideas:
        http://microship.com/bobstuart/coroplastarticle.html

        There may be other areas besides the hull where coroplast could be
        utilized.

        Bill


        --- In flapdoodle_dinghy@yahoogroups.com, "rwdavis0" <rwdavis0@...> wrote:
        >
        > Having just ordered the FD plans last week I'm sorting through the
        > options and thinking about construction. Has anyone any thoughts on
        > using 1/4" coroplast (corrugated plastic panels used for signs,
        > greenhouses, etc.) sandwiched between 1/8" plywood for the hull?
        >
        > If the edges were caulked I imagine some additional buoyancy would be
        > added, although 1/2" total thickness might be too much to lace
        > together. Maybe just just 1/8'ply on the outside/ coroplast in the
        > middle and Dacron fabric in the inside for 3/8'+ thickness?
        >
        > Bob Davis
        > (ps. I have (3) 4x8 sheets of coroplast in the garage for a greenhouse
        > project that I hope my wife has forgotten about.)
        >
      • Dave
        I would hesitate to use this material for one rason. Since it is made out of polypropylene it will be virtually impossible to bond to anything. Polypropylene
        Message 3 of 12 , Aug 4, 2007
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          I would hesitate to use this material for one rason. Since it is made
          out of polypropylene it will be virtually impossible to bond to
          anything. Polypropylene resists almost all high strength glues and to
          date the only thing that works is a very expensive 2 part glue from 3m
          that acts as a vulcanizer. As a matter of fact, I use polypropylene
          sheets when laying up epoxy/glass parts because I know that the epoxy
          will never stick. The only other way to bond poly is to bond it to
          itself using "plastic welding". You could try to laminate it to the
          plywood mechanically but that doesn't sound too good for the long run.

          If your goal is to increase stiffness and add flotation (though the
          plywood will float on its own) I would try using sheets of 1/8" foam
          and epoxy coating either dynell fabric or glass fiber to it to bring
          it up to 1/4". Home depot also sells 1/16" 4x8 sheets of pree formed
          fiberglass sheets for about $27 each. You could laminate 2 sheets of
          that to foam with epoxy (don't use polyester for this, not a strong
          enough glue bond and it will melt foam usually). Sadly at this point,
          for the money I would make it out of top grade marine ply and call it
          quits...

          PS. Bill, why all the water proof glues instead of epoxy for the builds?
        • Bill
          Excellent points Dave. Thanks for enlightening us. As for why I have not mentioned epoxy... I have not used any, so can t say one way or the other. The
          Message 4 of 12 , Aug 4, 2007
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            Excellent points Dave. Thanks for enlightening us.

            As for why I have not mentioned epoxy... I have not used any, so can't
            say one way or the other. The Elmer's Ultimate polyurethane gives me
            the bonding (even to aluminum) and has some flexibility. As a plus, it
            expands to fill any voids.

            Because epoxy has a hardener that is an oxidizer, it is not (usually)
            recommended for aluminum. I have seen some epoxies that are meant for
            aircraft. My friend at NASA showed me some of the problems with those
            and the epoxy primer paint.

            Anyhow, I hesitate to switch from something I am happy with.

            I don't want to give the impression there is an aluminum Flapdoodle in
            the works, but I did use aluminum angle on the X-Doodle. I hope to
            incorporate it further in other areas as an option since it works so well.

            One e-mail I got recently from a builder in South America asked if the
            FD hull could be made from aluminum sheet with wood trim. Maybe we
            will see an aluminum version.

            Bill


            --- In flapdoodle_dinghy@yahoogroups.com, "Dave" <dave@...> wrote:
            >
            > I would hesitate to use this material for one rason. Since it is made
            > out of polypropylene it will be virtually impossible to bond to
            > anything. Polypropylene resists almost all high strength glues and to
            > date the only thing that works is a very expensive 2 part glue from 3m
            > that acts as a vulcanizer. As a matter of fact, I use polypropylene
            > sheets when laying up epoxy/glass parts because I know that the epoxy
            > will never stick. The only other way to bond poly is to bond it to
            > itself using "plastic welding". You could try to laminate it to the
            > plywood mechanically but that doesn't sound too good for the long run.
            >
            > If your goal is to increase stiffness and add flotation (though the
            > plywood will float on its own) I would try using sheets of 1/8" foam
            > and epoxy coating either dynell fabric or glass fiber to it to bring
            > it up to 1/4". Home depot also sells 1/16" 4x8 sheets of pree formed
            > fiberglass sheets for about $27 each. You could laminate 2 sheets of
            > that to foam with epoxy (don't use polyester for this, not a strong
            > enough glue bond and it will melt foam usually). Sadly at this point,
            > for the money I would make it out of top grade marine ply and call it
            > quits...
            >
            > PS. Bill, why all the water proof glues instead of epoxy for the builds?
            >
          • rwdavis0
            Thanks for the input, guys. Maybe for my first effort I ll stick with plywood. Bob Davis
            Message 5 of 12 , Aug 4, 2007
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              Thanks for the input, guys. Maybe for my first effort I'll stick with
              plywood.
              Bob Davis
            • sae140
              ... well. ... In case it s of any interest to anyone: I ve had success with bonding aluminium spacing collars to the outside of yacht masts, where the normal
              Message 6 of 12 , Sep 6 1:16 AM
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                --- In flapdoodle_dinghy@yahoogroups.com, "Bill"
                <flapdoodle_dinghy@...> wrote:
                >
                > Excellent points Dave. Thanks for enlightening us.
                >
                > As for why I have not mentioned epoxy... I have not used any, so can't
                > say one way or the other. The Elmer's Ultimate polyurethane gives me
                > the bonding (even to aluminum) and has some flexibility. As a plus, it
                > expands to fill any voids.
                >
                > Because epoxy has a hardener that is an oxidizer, it is not (usually)
                > recommended for aluminum. I have seen some epoxies that are meant for
                > aircraft. My friend at NASA showed me some of the problems with those
                > and the epoxy primer paint.
                >
                > Anyhow, I hesitate to switch from something I am happy with.
                >
                > I don't want to give the impression there is an aluminum Flapdoodle in
                > the works, but I did use aluminum angle on the X-Doodle. I hope to
                > incorporate it further in other areas as an option since it works so
                well.
                >
                > One e-mail I got recently from a builder in South America asked if the
                > FD hull could be made from aluminum sheet with wood trim. Maybe we
                > will see an aluminum version.
                >
                > Bill
                >
                >


                In case it's of any interest to anyone:
                I've had success with bonding aluminium spacing collars to the outside
                of yacht masts, where the normal mode of attachment is rivetting (I
                wanted to avoid drilling holes at any cost), and also attaching
                internal strengthening sleeves inside aluminium masts using epoxy.
                The latter is a well-proven technique used by commercial spar makers
                who use the epoxy as a lubricant (!) whilst forcing the sleeve into
                position using hydraulic rams.

                The attachment process itself is known as wet-scouring, and involves
                wetting with epoxy glue the cleaned and pre-scoured surfaces to be
                bonded, then gently scouring each area with a wire brush or s/s
                scouring pad *through* the epoxy whilst it is still wet. This ensures
                that the epoxy attaches directly to the aluminium metal, and not to
                any surface oxide. Any anodising should be removed from the outset.

                I've subjected such joints to numerous "freezing through to 140
                degrees F" cycles without any failures ... (yet).

                The choice of epoxy is important: some products set glass-hard and I
                wouldn't recommend such brittle adhesives where flexing occurs. In
                Britain, Araldite 'Rapid' is fine, Araldite 'Precision' is not.
                General layup epoxy resin from ABL Stevens (www.resin-supplies.co.uk)
                is my preferred 'goop'. Can't comment on the West System - I've got
                some, but haven't used it yet.

                So - if anyone is contemplating joining sheet ally for folding boat
                use, it might be worth considering epoxy (?) - but DO subject some
                test-pieces to destruction first ...

                Polyurethane glues sound interesting - I'll search around for some to
                test.

                'best, Colin
              • Bill
                Thanks for the tip Colin. Yes I am very interested. I heard more from the fellow who wanted to build an aluminum Flapdoodle. Turns out he is in high school and
                Message 7 of 12 , Sep 6 2:13 AM
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                  Thanks for the tip Colin. Yes I am very interested.

                  I heard more from the fellow who wanted to build an aluminum
                  Flapdoodle. Turns out he is in high school and wanted it as a shop
                  project. His plan was to use the same thickness aluminum as wood,
                  I.E., 5mm aircraft aluminum for the hull panels. I doubt that I would
                  be able to lift it.

                  A bit of trivia... The reason we call it aluminum and everyone else
                  says aluminium, is because there was a typo in the advertising when
                  ALCOA first went into business. Money was short, so they left the typo
                  in, and it became known as aluminum in the U.S..

                  Bill


                  >
                  > In case it's of any interest to anyone:
                  > I've had success with bonding aluminium spacing collars to the outside
                  > of yacht masts, where the normal mode of attachment is rivetting (I
                  > wanted to avoid drilling holes at any cost), and also attaching
                  > internal strengthening sleeves inside aluminium masts using epoxy.
                  > The latter is a well-proven technique used by commercial spar makers
                  > who use the epoxy as a lubricant (!) whilst forcing the sleeve into
                  > position using hydraulic rams.
                  >
                  > The attachment process itself is known as wet-scouring, and involves
                  > wetting with epoxy glue the cleaned and pre-scoured surfaces to be
                  > bonded, then gently scouring each area with a wire brush or s/s
                  > scouring pad *through* the epoxy whilst it is still wet. This ensures
                  > that the epoxy attaches directly to the aluminium metal, and not to
                  > any surface oxide. Any anodising should be removed from the outset.
                  >
                  > I've subjected such joints to numerous "freezing through to 140
                  > degrees F" cycles without any failures ... (yet).
                  >
                  > The choice of epoxy is important: some products set glass-hard and I
                  > wouldn't recommend such brittle adhesives where flexing occurs. In
                  > Britain, Araldite 'Rapid' is fine, Araldite 'Precision' is not.
                  > General layup epoxy resin from ABL Stevens (www.resin-supplies.co.uk)
                  > is my preferred 'goop'. Can't comment on the West System - I've got
                  > some, but haven't used it yet.
                  >
                  > So - if anyone is contemplating joining sheet ally for folding boat
                  > use, it might be worth considering epoxy (?) - but DO subject some
                  > test-pieces to destruction first ...
                  >
                  > Polyurethane glues sound interesting - I'll search around for some to
                  > test.
                  >
                  > 'best, Colin
                  >
                • David Kyrejko
                  wet scouring is also used for led and copper bonding with epoxy. With aluminium I usually would use an acid etch primer that makes for a nice toothy surface.
                  Message 8 of 12 , Sep 6 6:52 PM
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                    "wet scouring" is also used for led and copper bonding with epoxy.
                    With aluminium I usually would use an acid etch primer that makes for
                    a nice toothy surface. For lead scouring is the ONLY way. Going to be
                    doing this a lot when I reshape my keel this fall...
                  • Bob Slimak
                    Just for info purposes, West systems is advertising a new epoxy, G- Flex, that they say works on Aluminum, plastic, and wood. Have not tried any of it myself.
                    Message 9 of 12 , Oct 5, 2007
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                      Just for info purposes, West systems is advertising a new epoxy, G-
                      Flex, that they say works on Aluminum, plastic, and wood. Have not
                      tried any of it myself.
                      Bob


                      -- In flapdoodle_dinghy@yahoogroups.com, "sae140" <SAE140@...> wrote:
                      >
                      > --- In flapdoodle_dinghy@yahoogroups.com, "Bill"
                      > <flapdoodle_dinghy@> wrote:
                      > >
                      > > Excellent points Dave. Thanks for enlightening us.
                      > >
                      > > As for why I have not mentioned epoxy... I have not used any, so
                      can't
                      > > say one way or the other. The Elmer's Ultimate polyurethane
                      gives me
                      > > the bonding (even to aluminum) and has some flexibility. As a
                      plus, it
                      > > expands to fill any voids.
                      > >
                      > > Because epoxy has a hardener that is an oxidizer, it is not
                      (usually)
                      > > recommended for aluminum. I have seen some epoxies that are meant
                      for
                      > > aircraft. My friend at NASA showed me some of the problems with
                      those
                      > > and the epoxy primer paint.
                      > >
                      > > Anyhow, I hesitate to switch from something I am happy with.
                      > >
                      > > I don't want to give the impression there is an aluminum
                      Flapdoodle in
                      > > the works, but I did use aluminum angle on the X-Doodle. I hope to
                      > > incorporate it further in other areas as an option since it works
                      so
                      > well.
                      > >
                      > > One e-mail I got recently from a builder in South America asked
                      if the
                      > > FD hull could be made from aluminum sheet with wood trim. Maybe we
                      > > will see an aluminum version.
                      > >
                      > > Bill
                      > >
                      > >
                      >
                      >
                      > In case it's of any interest to anyone:
                      > I've had success with bonding aluminium spacing collars to the
                      outside
                      > of yacht masts, where the normal mode of attachment is rivetting (I
                      > wanted to avoid drilling holes at any cost), and also attaching
                      > internal strengthening sleeves inside aluminium masts using epoxy.
                      > The latter is a well-proven technique used by commercial spar makers
                      > who use the epoxy as a lubricant (!) whilst forcing the sleeve into
                      > position using hydraulic rams.
                      >
                      > The attachment process itself is known as wet-scouring, and involves
                      > wetting with epoxy glue the cleaned and pre-scoured surfaces to be
                      > bonded, then gently scouring each area with a wire brush or s/s
                      > scouring pad *through* the epoxy whilst it is still wet. This
                      ensures
                      > that the epoxy attaches directly to the aluminium metal, and not to
                      > any surface oxide. Any anodising should be removed from the outset.
                      >
                      > I've subjected such joints to numerous "freezing through to 140
                      > degrees F" cycles without any failures ... (yet).
                      >
                      > The choice of epoxy is important: some products set glass-hard and I
                      > wouldn't recommend such brittle adhesives where flexing occurs. In
                      > Britain, Araldite 'Rapid' is fine, Araldite 'Precision' is not.
                      > General layup epoxy resin from ABL Stevens (www.resin-
                      supplies.co.uk)
                      > is my preferred 'goop'. Can't comment on the West System - I've got
                      > some, but haven't used it yet.
                      >
                      > So - if anyone is contemplating joining sheet ally for folding boat
                      > use, it might be worth considering epoxy (?) - but DO subject some
                      > test-pieces to destruction first ...
                      >
                      > Polyurethane glues sound interesting - I'll search around for some
                      to
                      > test.
                      >
                      > 'best, Colin
                      >
                    • Bill
                      Thanks Bob. Any epoxy that has flex will be much appreciated by me. Bill
                      Message 10 of 12 , Oct 6, 2007
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                        Thanks Bob. Any epoxy that has flex will be much appreciated by me.

                        Bill

                        --- In flapdoodle_dinghy@yahoogroups.com, "Bob Slimak"
                        <otter55806@...> wrote:
                        >
                        > Just for info purposes, West systems is advertising a new epoxy, G-
                        > Flex, that they say works on Aluminum, plastic, and wood. Have not
                        > tried any of it myself.
                        > Bob
                        >
                      • witt_saw
                        Hi Bill, Four months ago I purchased the $25.00 sample kit of RIKA epoxy. www.rika.com. I mixed up a small test batch and was pleased with the results. The
                        Message 11 of 12 , Oct 8, 2007
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                          Hi Bill,
                          Four months ago I purchased the $25.00 sample kit of RIKA epoxy.
                          www.rika.com. I mixed up a small test batch and was pleased with the
                          results. The leftover 1/4" thick 3" dia. hocky puck that stayed in the
                          bottom of the mixing container was knocked out yesterday with
                          interesting results. It is very flexable, it can be bent in half both
                          ways without cracking. The only drawback was the strong odor. I've been
                          using MAS epoxy for 12 years and it is almost odorless.
                          The RAKA is half the price of MAS.
                          Regards,
                          Steve Witter

                          --- In flapdoodle_dinghy@yahoogroups.com, "Bill"
                          <flapdoodle_dinghy@...> wrote:
                          >
                          >
                          > Thanks Bob. Any epoxy that has flex will be much appreciated by me.
                          >
                          > Bill
                          >
                          > --- In flapdoodle_dinghy@yahoogroups.com, "Bob Slimak"
                          > <otter55806@> wrote:
                          > >
                          > > Just for info purposes, West systems is advertising a new epoxy, G-
                          > > Flex, that they say works on Aluminum, plastic, and wood. Have not
                          > > tried any of it myself.
                          > > Bob
                          > >
                          >
                        • Bill
                          Thanks Steve. I mentioned earlier i have used Polyurethane glue on aluminum, but it was glued to wood. I discovered that it does NOT glue aluminum to plastic.
                          Message 12 of 12 , Oct 8, 2007
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                            Thanks Steve.

                            I mentioned earlier i have used Polyurethane glue on aluminum, but it
                            was glued to wood. I discovered that it does NOT glue aluminum to
                            plastic. Never hardens. Perhaps there was not enough moisture to
                            activate it. Made quite a mess out of my work.

                            Bill

                            --- In flapdoodle_dinghy@yahoogroups.com, "witt_saw" <witt_saw@...> wrote:
                            >
                            > Hi Bill,
                            > Four months ago I purchased the $25.00 sample kit of RIKA epoxy.
                            > www.rika.com. I mixed up a small test batch and was pleased with the
                            > results. The leftover 1/4" thick 3" dia. hocky puck that stayed in the
                            > bottom of the mixing container was knocked out yesterday with
                            > interesting results. It is very flexable, it can be bent in half both
                            > ways without cracking. The only drawback was the strong odor. I've been
                            > using MAS epoxy for 12 years and it is almost odorless.
                            > The RAKA is half the price of MAS.
                            > Regards,
                            > Steve Witter
                            >
                            > --- In flapdoodle_dinghy@yahoogroups.com, "Bill"
                            > <flapdoodle_dinghy@> wrote:
                            > >
                            > >
                            > > Thanks Bob. Any epoxy that has flex will be much appreciated by me.
                            > >
                            > > Bill
                            > >
                            > > --- In flapdoodle_dinghy@yahoogroups.com, "Bob Slimak"
                            > > <otter55806@> wrote:
                            > > >
                            > > > Just for info purposes, West systems is advertising a new epoxy, G-
                            > > > Flex, that they say works on Aluminum, plastic, and wood. Have not
                            > > > tried any of it myself.
                            > > > Bob
                            > > >
                            > >
                            >
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